1. Field of the Invention
This invention relates to a tester which tests equipment of a hybrid fiber-coaxial network and, more particularly, to a tester having frequency adjustable transmit and receive frequencies.
2. Description of the Prior Art
A typical hybrid fiber-coaxial (HFC) network 2 for communicating data, such as cable television program material, is shown in FIG. 1. The HFC network 2 includes a receiving antenna 4 which receives RF signals which include program material from a satellite or microwave transmission station (not shown) and provides the RF signals to a fiber optic head end 6 via a coaxial cable 8. The fiber optic head end 6 converts the received RF signals into optical program signals that are supplied to a fiber optic network 10. A computer 12 is connected to the fiber optic head end 6 for monitoring and controlling the operation thereof.
Connected to an end of the fiber optic network 10 opposite the fiber optic head end 6 is a fiber optic node 141. The fiber optic node 141 converts the optical program signals received from the fiber optic network 10 into RF program signals that are supplied via 75 ohm coaxial cables 161-163 to subscribers 181-183 at frequencies between 50 and 750 MHz. Connected to the fiber optic node 141 is a power supply 201. The power supply 201 converts incoming AC power, supplied from power lines (not shown), into an AC power signal, preferably a 60 Hz square wave signal having an RMS voltage of 60 or 90 volts. The AC power signal is supplied by the power supply 201 to the fiber optic node 141 which includes a rectifier which converts the AC power signal into DC power usable by electronic circuitry of the fiber optic node 141.
Another fiber optic node 142 can be connected to the fiber optic head end 6 via the fiber optic network 10. Another power supply 202, similar to power supply 201, is connected between incoming AC power and the fiber optic node 142. The-fiber optic node 142 converts the optical program signals received from the fiber optic network 10 into RF program signals at frequencies between 50 and 750 MHz. The fiber optic. node 142 supplies the RF program signals to a line amplifier 24 via a 75 ohm coaxial cable 22. The line amplifier 24 amplifies the RF program signals and supplies the amplified RF program signals to a subscriber 28 via a 75 ohm coaxial cable 26.
The power supply 202 superimposes its AC power signal on the coaxial cable 22 extending between the fiber optic node 142 and the line amplifier 24. The line amplifier 24 includes a rectifier which converts the AC power signal on the coaxial cable 22 into DC power usable by electronic circuitry of the line amplifier 24. Alternatively, the power supply 202 is connected to the line amplifier 24 and the fiber optic node 142 receives its AC power signal from the power supply 202 via the line amplifier 24 and coaxial cable 22.
A telephony network 30 supplies data signals and/or telephony signals to the fiber optic head end 6 via telephony lines 32. The fiber optic head end 6 converts the data signals and/or telephony signals received from the telephony network 30 into optical data/telephony signals that are supplied to the fiber optic network 10. One or more of the fiber optic nodes 141 and 142 receives the optical data/telephony signals and converts the received optical data/telephony signals into RF data/telephony signals which are supplied to the subscribers 181-183 and 28 via the coaxial cables 161-163 and 26 at frequencies between 50 and 750 MHz.
The subscribers 181-183 and 28 can also generate RF data/telephony signals which are supplied to the fiber optic nodes 141 and 142 at frequencies between 5 and 40 MHz. The fiber optic nodes 141 and 142 convert the data signals and/or telephony signals received from the subscribers 181-183 and 28 into optical data/telephony signals that are supplied to the fiber optic head end 6 via the fiber optic network 10. The fiber optic head end 6 converts the optical data/telephony signals received from the fiber optic nodes 141 and 142 into data signals and/or telephony signals that are supplied to the telephony network 30.
As can be seen, the HFC network 2 can be utilized to supply data signals and/or telephony signals between the telephony network 30 and subscribers 181-183 and 28 and can be utilized to supply cable television program material from the antenna 4 to the subscribers 181-183 and 28.
Proliferation of HFC networks has increased the need for cable service providers to quickly and accurately identify problems with equipment of such HFC networks. Specifically, if one or more pieces of equipment, such as the fiber optic nodes 141 or 142, the power supplies 201 or 202 and/or the line amplifier 24, are inoperative or are operating at a reduced performance level, the cable operator is often unaware of the problem until a subscriber reports the problem. Thereafter, a craftsperson must be dispatched to identify and repair the faulty component.
It is an object of the present invention to provide a tester which tests test points of equipment of the HFC network and which reports test results to a central data collection computer. It is an object of the present invention to provide a frequency agile tester which can be connected to test points of equipment of the HFC network and which has selectable transmit and receive frequencies which enable bidirectional communication between the tester and a central data collection computer. Still other objects of the invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.
Accordingly, we have invented a frequency agile (F/A) transponder which is connectable to at least one test point of equipment of a hybrid fiber-coaxial network. The F/A transponder includes a receiver configured to be connected to a first cable of the HFC network. The receiver receives from the first cable signals modulated around a receive center frequency and obtains from the received signals receive data. A controller is connected to receive the receive data from the receiver. The controller is configured to detect an electrical condition at the at least one test point. The controller compares the detected electrical condition to a predetermined electrical condition and produces as a function of the comparison transmit data. A transmitter is connected to receive from the controller the transmit data. The transmitter is configured to produce from the transmit data signals modulated around a transmit center frequency. The transmitter supplies the signals modulated around the transmit center frequency to one of the first cable and a second cable of the HFC network. The receive center frequency and the transmit center frequency are different frequencies. In response to a frequency change signal received by the receiver on the first coaxial cable at the receive center frequency, the receiver changes to receive signals at another receive center frequency or the transmitter changes to transmit signals at another transmit center frequency.
We have also invented a hybrid fiber-coaxial (HFC) network for communicating data between a fiber optic head end and a subscriber. The HFC network includes a fiber optic node connected between a fiber optic network and a conductive cable. The fiber optic node is configured to receive optical signals via the fiber optic network and to convert the received optical signals into signals modulated around a receive center frequency. The fiber optic node supplies to the conductive cable the signals modulated around the receive center frequency. The fiber optic node also receives from the conductive cable signals modulated around a transmit center frequency and converts the received signals modulated around the transmit center frequency into optical signals that are supplied to the fiber optic network. A power supply supplies electrical power to the fiber optic node. A frequency agile transponder is connected to the conductive cable and a test point in one of the fiber optic node and the power supply. The frequency agile transponder is configured to detect an electrical condition at the test point. The frequency agile transponder receives from the conductive cable the signals modulated around the receive center frequency and supplies to the conductive cable the signals modulated around the transmit center frequency. In response to receiving via the coaxial cable a frequency change command signal modulated around the receive center frequency, the frequency agile transponder adapts itself to receive signals modulated around another receive center frequency or to supply signals modulated around another transmit center frequency.
We have also invented a method of communicating over a conductive cable of a hybrid fiber-coaxial network. In the method, a frequency change command signal modulated around a first receive center frequency is received on the conductive cable. In response to receiving the frequency change command signal, (i) the detection on the conductive cable of signals modulated around the first receive center frequency is terminated and signals modulated around a second receive center frequency are detected on the conductive cable or (ii) transmitting on the conductive cable signals modulated around the first transmit center frequency is terminated and signals modulated around a second transmit center frequency are transmitted on the conductive cable.